Artificial respiration and cardiopulmonary resuscitation (CPR) are life-saving measures that supply necessary oxygen (O.sub.2) to the blood and tissues of a patient who has experienced a cessation of normal breathing and a regular heart beat. Artificial respiration provides O.sub.2 to a victim that has stopped breathing. Typically, artificial respiration can involve mouth-to-mouth ventilation (MTMV). In MTMV oxygen is provided to the victim through the expiration of the rescuer. To initiate the MTMV procedure, the rescuer opens the air-way of the victim by tilting the head of the victim back and pulling the jaw forward. The rescuer forms a seal over the mouth, or mouth and nose, of the victim with the rescuer's mouth. The rescuer then exhales into the mouth of the victim. The rescuer's exhalation is forced into the lungs of the victim and provides the victim with needed O.sub.2.
Cardiopulmonary resuscitation combines mouth-to-mouth ventilation with compressions to the thorax or chest. The chest compressions push blood through the circulatory system to provide oxygen to the tissues including the heart and to remove carbon dioxide and stimulate the heart. Both procedures are used to restore normal respiratory and circulatory function or to sustain the life of a victim until adequate medical attention can be obtained.
References to procedures for artificial respiration and mouth-to-mouth ventilation have been noted for thousands of years; CPR, however, has only become an accepted practice within about the last 30 years (Hermreck, 1988; BeBard, 1980). Today, both procedures are mainstays in emergency medical situations.
Both CPR and artificial respiration can involve mouth-to-mouth contact between rescuer and victim. Therefore, concerns have arisen as to the possible transmission of communicable diseases during these life-saving procedures. Concerns have heightened recently with the emergence of AIDS. Although there have been no reported incidences of health care workers becoming HIV-positive after administering CPR to an AIDS patient, a recent survey reports that 93% of nurses surveyed would hesitate to give CPR to a patient with AIDS (Michael et al; 1992). In a survey of CPR instructors, 71% said that their attitudes about providing CPR to strangers have changed as a result of the AIDS epidemic. Forty percent of those instructors surveyed who had administered CPR in the previous three years admitted that they did hesitate before administering CPR to a victim, and over half cited a fear of disease as the cause of that hesitation (Ornato et al., 1990).
To avoid physical contact during artificial respiration and CPR, many first-aid kits now include a mask that provides a physical barrier between the mouth of the victim and the mouth of the rescuer. There are three basic types of masks routinely used for this purpose. U.S. Pat. No. 5,095,898 describes one such mask. The three main types are bag-valve masks, hand-held masks, and lay-on barrier masks. The bag-valve mask, or manual resuscitation bag, has a molded facepiece which is contoured to cover the nose and mouth of the victim. The facepiece is impermeable to air so that if properly sealed all air administered to the victim is ultimately forced into the upper airway of the victim and then into the lungs. A bag is attached to the facepiece and holds the air for ventilation. The bag-valve mask eliminates close contact between the rescuer and victim, but can prove cumbersome for a single rescuer trying to pump the bag and keep the mask sealed tightly over a victim's nose and mouth. Further, bag-valve masks usually deliver sub-optimal ventilation volumes, probably due to the lack of a proper seal.
Hand-held masks have a facepiece similar to the contoured facepiece of the bag-valve mask, but do not have a bag for ventilation. The rescuer exhales directly into an orifice in the mask. Hand-held masks therefore require more intimate contact between the rescuer and victim, but still provide a physical barrier.
Lay-on barrier masks are pliable sheets that act as a physical barrier between the mouth of the victim and the mouth of the rescuer. Lay-on barrier masks provide the greatest ventilation volume of the three types of masks. However, lay-on masks do not provide an adequate barrier to prevent contamination should a victim vomit into the mask. Further, these masks can only be used for mouth-to-mouth ventilation and cannot be connected to a bag for manual ventilation.
Because of the risks associated with mouth-to-mouth contact, debates have arisen as to the necessity of ventilating the victim during CPR. Ventilation has been found to be necessary, however, for successful resuscitation (Idris et al, 1994a; Idris et al., 1994b). Proper ventilation affects the acid-base balance as well as oxygenation of the blood of the victim, and assists in successful recovery (Idris et al., 1994b; Idris et al., 1992). Recent studies have shown that hypoxia (below normal levels of O.sub.2) and hypercarbia (above normal levels of CO.sub.2) in ventilating gas have independent adverse effects on resuscitation from cardiac arrest (Idris et al., 1994a; Idris et al., 1994b). The air we normally breath is approximately 21% O.sub.2 and 0.033% CO.sub.2. The composition of the air or gas exhaled by a rescuer is approximately 17-18% O.sub.2 and 3.5-4% CO.sub.2 (Wenzel et al., 1994a; Wenzel et al., 1994b). Percentages of CO.sub.2 can be higher in one-rescuer CPR as opposed to two-rescuer situations. This is probably due to the greater work load that the single rescuer performing CPR must endure. Therefore, the gas composition delivered by a rescuer to a victim during CPR is both hypoxic and hypercarbic when compared to the air we normally breath. High levels of CO.sub.2 have further been found to cause the inhibition of spontaneous contractions of myocardial cells in culture. This suggests that high levels of CO.sub.2 may be dangerous to the heart (Becker et al., 1993).
Anesthesia machines use certain chemicals to remove carbon dioxide from gases given to a patient. Pasternak (U.S. Pat. No. 4,491,130) describes an emergency respirator which removes CO.sub.2 from inhaled air when the surrounding air becomes climatically unfavorable. The respirator of Pasternak is for a user who is breathing independently. The respirator comprises a heat storage mass which captures body heat lost by the user during exhalation, and stores the heat to be supplied back to the user upon inhalation. The respirator provides the user with breathable air and prevents heat loss during respiration.